As a relating technology, as exemplified in FIG. 1 of Japanese Patent Application Laid-Open Publication No. 2010-144312 (Patent Literature 1), there is a cloth-like heater in which electroconductive string is incorporated into a fiber product and the fiber product is warmed as a whole by heat generated when the electroconductive string is energized. By energizing an electroconductive string 130 of an intermediate layer, it is possible to uniformly warm the whole of the surface.